1. Field of Invention
The present invention relates to an image processing apparatus and an image processing method. More particularly, the present invention relates to an image processing apparatus and an image processing method capable of enhancing picture quality of images by extracting additional information from non-standard signals without an error.
2. Description of the Related Art
Image processing apparatuses, such as TVs, receive image signals including predetermined images, according to a digital TV broadcast, a cable TV broadcast, and the like, from a broadcasting station. Image processing apparatuses also perform image processing on the received image signals, thus outputting the images. Image processing apparatuses can receive image signals from various image apparatuses, such as, a VCR, a DVD, and the like, and perform image processing on the image signals.
FIG. 1 is a block diagram of a conventional image processing apparatus 1. The image processing apparatus 1 includes a video decoder 10 for receiving and decoding various image signals, a deinterlacer 20 for converting the decoded image signals into progressive signals, a scaler 30 for performing image processing in order to appropriately display the progressive signals, and a display unit 40 for displaying the image-processed signals.
The video decoder 10 includes two analog-to-digital converters (ADCs) 11 and 12 for receiving analog signals, such as, a Composite Video Baseband Signal (CVBS), a Y signal (luminance signal), a C signal (chrominance signal), and a RGB signal, and converting the analog signals into digital signals. The video decoder 10 also includes a comb unit for dividing the CVBS into a luminance signal and a chrominance signal; a color space transform unit 14 for converting the RGB signal into a YUV signal; a color decoder 15 for decoding encoded chrominance signals into original color signals; a soft mixer 16 for mixing the CVBS and the RGB signal; an image enhancer 17 for adjusting the sizes or offsets of signals; and a format transformer 19 for transforming the format of a signal required by a system to be output.
An image signal input to the video decoder 10 can include various additional information, as well as information regarding an image to be displayed on the display unit 40. For example, the additional information includes caption data (hereinafter, referred to as “closed caption data”) for auditory challenged, a teletext, wide screen signal, vertical interval time code, and the like. The additional information can be included in the image signal in a vertical blanking interval (VBI). Particularly, the closed caption data is encoded in a 21st and/or 284th line of the image signal in accordance with a National Television System Committee (NTSC) television system.
The video decoder 10 of the conventional image processing apparatus 1 includes a VBI slicing unit 18 in correspondence to the additional information. The VBI slicing unit 18 receives and decodes the image signal output from the ADC 11, extracts additional information from the decoded image signal, and outputs the additional information to the format transformer 19. FIG. 2 is a waveform diagram illustrating the 21st line including closed caption data in a CVBS 50. A portion of the image signal 50 corresponding to the 21st line includes a color burst signal 52, a clock run-in signal 53, and caption data 54, which is additional information. The clock run-in signal 53 is a sinusoidal signal with maximal and minimal values respectively quantized to logic values “1” and “0,” and has 7 waveforms with a clock frequency 503 KHz. The caption data 54 has a start bit “001” and 16 bits of data (two ASCII data and two parities). In FIG. 2, reference numeral 51 represents a synchronous signal. The VBI slicing unit 18 decodes the input image signal in synchronization with the clock run-in signal 53, thus extracting the caption data 54 from the image signal.
The image signal input to the video decoder 10 may be a standard signal based on an international standard, or a non-standard signal not based on the international standard. The non-standard signal may be an output signal of a VCR, or an RF broadcasting signal used in some regions of America. The non-standard signal can include additional information, such as the caption data 54, other than an image. However, the output signal of the VCR, among the non-standard signals, can have an active video signal, instead of null data, in the signal's 284th line when the closed caption data 54 is encoded in the 21st line of the VCR output signal, which is different from standard signals in which null data are encoded in their 284th lines. The waveform of the 284th line of the VCR output signal is shown in FIG. 3. In FIG. 3, reference numeral 60 represents an active video signal.
The VBI slicing unit 18 attempts to decode and extract the corresponding signal in the 284th line, in the same manner as the operation of decoding the closed caption data 54 in the 21st line. However, since the active video signal has a format different from the closed caption data 54, an error occurs when the VBI slicing unit 18 extracts caption data. Thus, broken characters are displayed instead of correct caption data, although the caption data is extracted.
Accordingly, there is a need for an improved image processing apparatus and image processing method that extracts caption data without producing errors.